Diode-laser second-derivative modulation spectrometry is a simple means of measuring trace concentrations of small molecules in the gas phase. For a setup with a reference cell used both for laser frequency locking and as a concentration standard, the calibration algorithm is developed for the general case of nonvanishing nonlinear terms in the power expansion of Beer’s law in both the sample and reference channel. A practical example is given.
© 1984 Optical Society of America
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